It is generally known that crystalline forms greatly affect drug's quality. Different crystalline forms may have remarkable difference in appearance, solubility, melting point, dissolution profile, bioavailability and so on, thus affect drug's stability, bioavailability and efficacy. Therefore, it is of great significance to develop novel and more suitable crystalline forms for drug development.
Ponesimod (Compound I) is a selective S1P1 receptor modulator developed by Actelion. The drug achieved positive results in phase II mid-stage study for the treatment of moderate-to-severe chronic plaque psoriasis, and will be studied in phase III for the treatment of psoriasis.

At present, CN100567275 C discloses a preparation method of Compound I in example 85, which is amorphous according to disclosure of CN102177144 B.
Additionally CN102177144 B discloses Form A, Form C, Form III and Form II of Compound I. Studies show that Form III has poor crystallinity, and will transform to Form II at room temperature; Form II is difficult to repeat and contains a certain amount of propionic acid; thermodynamic stability of Form A is inferior to Form C. Compared with them all, Form C is suitable for drug development, but its solubility is unsatisfactory.